The present invention relates to a fixing apparatus for use, for example, in an image forming apparatus.
This type of fixing apparatus is disclosed, for example, in Jpn. Pat. Appln. KOKAI Publication Nos. 2002-49261, 2001-188427 and 10-63126.
A fixing roller of the fixing apparatus disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2002-49261 has a cylindrical rigid body in which a layer of a lower heat conduction material, a conductive layer of an electroconductive material and a mold releasing layer are sequentially formed on an outer side of the rigid body. Near the fixing roller, an induction heating source is provided opposite to the outer peripheral surface of the roller.
By inductively heating the conductive layer of the fixing roller by means of the induction heating source it is possible to heat the fixing roller in a short time to a desired temperature.
A fixing apparatus disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2001-188427 includes a heating member with a conductive layer formed on a hollow member and a magnetic field generating means arranged outside the heating member and generating a varying magnetic field on the conductive layer to achieve warm-up in a short time.
A fixing apparatus disclosed in Jpn. Pat. Appln. KOKAI Publication No. 10-63126 is of such a type that a conductive wire (Litz wire) is arranged around a peripheral surface portion other than a nip portion between a heating roller and a pressing roller and, by connecting the conductive wire to a high frequency oscillation section and applying a high-frequency current, it is possible to heat the surface of the heating roller. By applying heat to the surface of the heating roller, the fixing apparatus can reduce an energy loss and ensure a short rise time.
In the prior art, however, no consideration has been paid to the following problems likely to occur in a practical application.
1. How to deal with a breakage, separation, etc., of the layers (constituent elements) of the fixing roller resulting from their deterioration, etc., caused by prolonged use, etc.
2. How to deal with a slip caused between the layers.
3. Consideration to be paid to the positioning of a sheet separation blade when the fixing roller is deformed.
4. An adjustment of the roller hardness, heat conductivity and heat capacity, as well as an improvement of a resulting separation, fixability and warming-up time obtained by changing the material and layer thickness in the case where a heating rotation body and pressing rotation body are of such a type that a conductive layer is formed on their elastic layer.